This invention relates to an electric heater system for heating-diesel fuel contained within tanks used to supply fuel to a diesel engine. The engine could be located e.g. in a truck, construction equipment, mining equipment, farm equipment (a tractor), or ship. The heating system is used to prevent or minimize jelling of the fuel and the build-up of wax crystals in the fuel when the tank is exposed to winter or arctic temperatures.
In some respects this invention is similar to inventions disclosed in U.S. Pat. No. 4,424,422 to Bell et al, U.S. Pat. No. 4,684,786 to Mann et al, U.S. Pat. No. 4,723,065 to H. Meyer, and U.S. Pat. No. 4,865,005 to E. Griffith. A principal object of the present invention is to heat the fuel in diesel fuel tanks so that the temperature in the tanks is substantially uniform throughout each tank, with minimum localized hot spots that could lead to carbonization of the fuel or an unsafe operating condition. Another object of the invention is to provide a heater system that operates effectively whether the tank is full or substantially empty. In a preferred embodiment of the invention two separate tanks are provided for supplying fuel to a single engine. Each tank is equipped with a thermostatically controller heater system. Manual controls are provided for selectively connecting the tanks to the engine.
The invention contemplates the use of an immersion heater in the lower portion of each diesel fuel tank. Separate temperature sensors are located in the upper portion of each tank and in the lower portion of each tank for independently controlling the heater. A liquid level responsive device within each tank selectively connects the sensors to the respective heater, such that when the tank is substantially full the upper sensor controls the heater, and when the tank is less than one half full the lower sensor controls the heater. The aim is to achieve a fairly uniform liquid temperature whatever the quantity of liquid in each tank.